Coaxial line oscillator



QELHHUH Hwuau July 27, 1954 J. H. SCHAEFER COAXIAL LINE OSCILLATOR 2 Sheets-Sheet l 6 4 9 l l 3 y a M d 8 1 1 F wow INVENTOR. JAMES H. SCHAEFER ATTORNEY July 27, 1954 J. H. SCHAEFER ,0

COAXIAL LINE OSCILLATOR I Filed May 31, 1946 2 Sheets-Sheet 2 TO FILAMENT VOLTAGE M 7 m1 WWW 74 6:

ANTENNA TO B-AND INVENTOR. JAMES H. SCHAEFER W ATTORNEY Patented July 27, 1954 UNITED STATES PATENT OFFICE 7 Claims. (01. 250-36) (Granted under Title 35, U. S. Code (1952),

see. 266) This invention relates in general to a high frequency oscillator and more specifically to a novel type of line-controlled high frequency oscillator.

It is an object of this invention to provide a compact, line-controlled high frequency oscillator.

It is a further object of this invention to provide a line-controlled high frequency oscillator which is readily tunable over a range of frequencies and which suffers a minimum change in power output throughout its tuning range.

Still another object of this invention is to provide a line-controlled oscillator in which a series of cylindrical line sections are so arranged that one of such line sections encompasses the rest of the assembly to thereby provide a protective housing as well as a radio frequency shield for the oscillator.

Other objects and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the invention and in which:

Fig. 1 is a simplified illustration of one embodiment of the invention.

Figs. 2 and 3 show the approximate electrical diagram of the embodiment illustrated in Fig. 1.

Fig. 4 is an illustration in more detail of the embodiment shown in Fig. 1.

In accordance with the present invention, an oscillator is constructed with tuned-line sections arranged in such a manner as to provide a compact and rugged assembly. As illustrated in the preferred embodiment, a combination of two coaxial lines are used as the grid-plate tuned element and a similar combination as the cathodeplate tuned element arranged one within another. Such an arrangement is advantageous in that the outer conductor of the inner coaxial line and the inner conductor of the outer coaxial line may be united into a single conductor, since both may be connected, as hereinafter described, to one electrode of the oscillator tube. It is also contemplated that the outer conductor of the outer coaxial line will be at ground potential with respect to direct voltages, thus eliminating the hazards and disadvantages of having exposed conducting surfaces at high direct potentials to ground.

In Fig. 1, to which reference is now had, there is shown an oscillator arrangement whereby two coaxial lines, concentric with each other, form a tuned element. This arrangement includes a triode vacuum tube ll, of a type well known in the art, having a plate l5, grid I! and cathode I8.

2 Circumscribing the tube H is a hollow cylinder 24 which is open at both of its extremities, and coaxially aligned with a second hollow metal cylinder 20 which is closed at both of its extremities 22 and 23. The tube H i located inside the hollow metal cylinder 24 such that the tube is concentric with the cylinder. Its plate I 5 is connected to this cylinder by means of a metallic disc 29 which extends out from the tube perpendicular to the axis of the cylinderand which is connected to the cylinder about its complete circumference. The terminals for the cathode l 8 and grid ll of the triode l I extend axially from the tube envelope and are connected to the rodlike conducting members 19 and [6, respectively, which extend axially outward from the inner walls of end plates 22 and 23 of cylinder 20. Although the hollow cylinder 20 fits over the cylinder 24, no direct electrical contact is maintained between these cylinders. Thus, two double-coaxial lines are formed, one between cathode and plate and the other between grid and plate, each of these lines consisting of a coaxial line within a coaxial line. The inner line of the two coaxial lines between cathode and plate consists of the conductor l9 and the portion of the hollow cylinder 24 to the right of the plate connector 29, as shown in Fig. 1. The outer coaxial line between cathode and plate of the tube ll consists of the same portion of the cylinder 26 as the inner conductor and a portion of the cylinder 20 as the outer conductor. If the cylinder 26 be considered 'as an extension of the conductor l9, it will be seen that whereas initially the conductor [9 is the inner conductor of the coaxial line with the cylinder 24 serving as the outer conductor, subsequently the cylinder 24 becomes the inner conductor and the extension of the conductor IS, in other words the hollow cylinder 26, serves as the outer conductor of the line. A coaxial line within a coaxial line serves also as the grid-plate tuned element. The grid conductor [6 may be considered as the inner conductor of a coaxial line having as its outer conductor the portion of the cylinder 24 to the left of the plate connector 29 as shown in Fig. 1, While the outer coaxial line may have the same portion of the cylinder 24 and a portion of the cylinder 20 as inner and outer conductors, respectively. The approximate paths of thegrid-plate coaxial line may be considered to be indicated by arrows 26 and 26A, while arrows 25 and 25A indicate the parallel paths of the cathode-plate coaxial line. If, now, the meeting point of the coaxial lines between cathode and plate and between grid and plate of the tube l I is considered to be along a plane AA, which plane may be found through the use of a neon bulb, and along this plane there exists a voltage node, the point of intersection of this plane with the surface of the cylinder 24 may serve as the point of application of positive voltage to the plate I of the oscillator tube II. If, then, the conductor carrying such a voltage enters the oscillator through a hole in the cylinder at a point 21 which lies on the intersection of the plane AA with the cylinder 20, this cylinder may be at ground potential with respect to direct voltage.

Fig. 2 shows a circuit which closely parallels the actual electrical circuit of the arrangement shown in Fig. 1. In this circuit diagram, the distributed constants of the coaxial lines are shown as equivalent inductances and capacitances comprising the tuned element I2 between grid and plate and the tuned element I3 between cathode and plate. The capacitance represents the interelectrode capacity between cathode and grid of the oscillator tube II and the capacitances I4 and 3| represent the cathodeplate and grid-plate capacitances, respectively. Because of the interaction of the interelectrode capacitances on the tuned elements I2 and I3, it is not necessary that these elements be resonant at the frequency of oscillation.

The circuit shown in Fig. 2 may be further simplified to the schematic diagram shown in Fig. 3. In order for the tube I I to oscillate, the combination of the condenser I4 and the tuned element I3, these being parallel to each other, must appear as a single capacitance such as the capacitance 32. Additionally, the capacitance 3| and the tuned element I2, both of which are parallel to each other, must appear as the inductance 33. It will thus be seen that the tuned element I2 should be tuned to a higher frequency than the tuned element I3 and the actual resonant frequency, in order that the tuned element I2 and the capacitance 3| may be replaced Iby an equivalent inductance 33. It will also be i seen that an ordinary circuit of the Colpitts type twill result.

Referring now to Fig. 4, there is shown in greater detail the arrangement of Fig. 1. As in Fig. 1, an oscillator tube I is shown, which comprises the glass envelope 44; the filament leads and 4|, with the lead 45 also serving as the cathode connection; the grid I1; and the plate I5, which has a large external surface and includes the cooling fins 42. Surrounding the tube II and concentric therewith is the hollow metal cylinder 24 which is open at both ends, and the hollow metal cylinder 20 having the end faces 22 and 23 envelope the cylinder 24 and the tube II and is concentric with them. Voltage is applied to the cylinder 24 at the point 2| by leading a conductor carrying such a voltage through the hole 21 in the cylinder 20. A conducting member I6 is attached to the grid I1 and extends, concentric with the cylinder 20, to the end face 23 of that cylinder, to which it is attached. Likewise, the conducting member I9 is connected between the cathode I8 and the end face 22 of the cylinder 20 and is concentric with the cylinder. The end face 22 may be removed by loosening the screws 40 and 48 which hold conductor I9 to the face 22 and the face 22 to the cylinder 20, so that easy access may be obtained to the tube II and other components. The cylinder 24 is coaxially supported inside cylinder 20 by means of a series of insulators 43 located perpendicular to the concentric axis of the hollow cylinders. Filament voltage is applied to the conductor 49, which is connected to the filament 4| such that it extends out beyond the end plate 22, and to the ground connection at the lower left side of the cylinder 20. Power for the antenna is collected by means of the loop 5| and is led from the oscillator by means of the coaxial cable 52 which passes through the hole 53 in the cylinder 20. As in Fig. l, a coaxial arrangement within a coaxial arrangement results, the plate-cathode tuned element consisting of the conducting member I9 and the hollow cylinders 24 and 20 and the plate-grid tuned element comprising the conducting member I6 and the portion of the cylinders 24 and 20 not used in connection with the plate-cathode tuned element. The oscillator circuit which results is again electrically similar to that shown in Fig. 3. However, since the frequency of oscillation is primarily determined by the grid-plate line, the frequency may be given a considerable range by varying the position of a metal disk 34 on the conducting member I6. The metal disk 34 is so constructed that although it does not touch the walls of the cylinder 2|] it is sufficiently close to these walls to provide such a change of impedance as to alter the oscillation frequency. Its position along the grid conductor I6 is varied by actuating a worm drive 35 which transmits the position to the disk 34 by means of the stud 36 riding in key way 4! and engaging worm 35. The worm drive itself is actuated by means including another worm gear 31 and a phenolic drive shaft 38 integral with the gear 31 and extending from the gear 31 to a point outside the walls of the hollow cylinder 20, at which point a knob 39 is fastened to the shaft 38 to facilitate gripping the shaft. The shaft held in position by means of the housing 46.

While certain preferred embodiments of this invention have been described, it is realized that many modifications and variations of this invention may be made and no limitations upon this invention are intended other than may be imposed by the scope of the appended claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

l. A radio frequency oscillator comprising, a vacuum tube having at least a grid, a cathode and a plate, a first metallic cylinder open at both ends and surrounding said tube, a second metallic cylinder closed at both ends and coaxially enclosing said open cylinder, a pair of conducting members extending respectively from the cathode and grid of said tube to the end faces of said closed cylinder, and means conductively connecting the plate of said tube to the wall of said open cylinder.

2. A radio frequency oscillator comprising a vacuum tube having at least a grid, a cathode and. a plate, a first metallic cylinder open at both ends and surrounding said tube, a second metallic cylinder of fixed dimensions closed at both ends and coaxially enclosing said open cylinder, a pair of conducting members extending respectively from the cathode and grid of said tube to the end faces of said second cylinder, and means conductively connecting the plate of said tube to the wall of said open cylinder.

3. A radio frequency oscillator comprising. a vacuum tube having at least plate, grid and cathode electrodes, the terminals of said cathode and grid electrodes extending axially from opposite ends of said tube, the terminal for said plate electrode extending normal to the tube axis, a first metallic cylinder open at both ends and surrounding said tube and concentric with the cathode and grid terminals of said tube, means conductively connecting the plate extensions of said vacuum tube to the wall of said first cylinder, a second metallic cylinder closed at both ends and coaxially enclosing said first cylinder, and a pair of conducting members extending axially out from the cathode and grid of the tube to the opposite end faces of said second cylinder.

4. A radio frequency oscillator comprising, a vacuum tube having at least a grid, a cathode and a plate, the terminals of said cathode and grid electrodes extending axially from opposite ends of said tube, the terminals for said plate extending normal to the tube axis, a metallic cylinder open at both ends and surrounding said tube, a second metallic cylinder closed at both ends and coaxially enclosing said open cylinder, a pair of conducting members extending from opposite ends of said second cylinder contacting respectively the grid and cathode electrodes of said tube, conducting members extending from the plate of said tube to the wall of said hollow open cylinder, means for introducing power to the plate of said tube through an opening in said closed cylinder, said last named opening positioned at the point of voltage node on said open cylinder.

5. A radio frequency oscillator comprising, a vacuum tube having at least a grid, a cathode and a plate, the terminals of said cathode and grid electrodes extending axially from opposite ends of said tube, the terminals for said plate extending normal to the tube axis, a first metallic cylinder open at both ends and surrounding said tube, a second metallic cylinder closed at both ends and coaxially enclosing said open cylinder, insulating means supporting said open and closed cylinders in coaxial relationship with each other, means for electrically connecting the plate of said tube to said open cylinder, conducting members extending from opposite ends of said second cylinder contacting respectively the grid and cathode electrodes of said tube, means for introducing power to the plate of said tube through an opening in said closed cylinder, said last named opening positioned at the point of voltage node on said open cylinder, and means grounding said closed cylinder.

6. In an oscillator substantially as described in claim 1, means for varying the frequency of oscillation, said means comprising, a metallic element connected to the grid conductor which extends from the grid of the vacuum tube, and means connected to said metallic element for varying the position of said metallic element on said grid conductor to thereby effectively vary the value of the distributed constants constituting the tuned element between grid and plate of said vacuum tube.

7. In an oscillator substantially as described in claim 1, means for varying the frequency of oscillation, said means comprising, a disc-shaped metallic element connected to the grid conductor which extends from the grid of the vacuum tube to an end face of the closed hollow cylinder, and means for varying the position of said metallic element on said grid conductor to thereby effectively vary the value of the distributed constants constituting the tuned element between grid and plate of said vacuum tube, said means including a worm and gear arrangement substantially housed in said grid conductor and a shaft extending therefrom to a point external from said closed cylinder to vary the position of said metallic element along said grid conductor.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,088,722 Potter Aug. 3, 1937 2,306,282 Samuel Dec. 22, 1942 2,400,753 Haeff May 21, 1946 2,408,355 Turner Sept. 24, 1946 2,408,927 Gurewitsch Oct. 8, 1946 2,431,273 Nergaard Nov. 18, 1947 2,443,907 Gurewitsch June 22, 1948 

